1. Field of the Invention
The present invention relates to mechanical seals and, more particularly, to a mechanical seal assembly of a cartridge type having means for maintaining alignment and preloading between the stationary and rotating portions of the seal assembly.
2. Description of the Background
Numerous different mechanical seals have been proposed to effect sealing around a shaft to prevent leakage of both sealing fluid and operating fluid from an enclosure from which the shaft extends. While mechanical seals employing a single biasing spring coil are known, typically, where high speeds are involved, multiple, small coil springs are used, the coil springs being circumferentially spaced around the rotary unit. Both compression springs and tension springs have been used as means to bias the rotating and stationary seal faces together.
To the extent known by the Applicant, in a case where the springs are used to bias the stationary seal member, and particularly where the springs are mounted externally of the process fluid, the springs are supported on their outside diameter, usually contained in pockets in a separate spring housing or the like that attaches to the main housing or gland of the seal, or in the main housing itself.
Mechanical seal designs employing compression springs that are supported on their outside diameter, e.g., in spring pockets in the main or a separate spring housing, frequently encounter problems because of clogging sources such as coking, oxidation, salts from fluids that crystallize, contaminants from slurries, etc. This clogging restricts the springs' ability to provide axial closing force to the seal face. Additionally, mechanical seals wherein the springs are located internally, i.e., in an area where they are contacted by any corrosive fluid (process fluid) that leaks past the seal, are subject to stress corrosion cracking.
In addition to avoiding the clogging and corrosion problems discussed above with respect to many prior art mechanical seal designs, it is also desirable that the biasing springs be subject to complete visual inspection while in service. If the springs are located in spring pockets or separate spring housings or disposed directly behind the seal element being biased, this becomes virtually impossible.
Accordingly, there remains a need for a mechanical seal design employing compression springs, especially compression springs that act to bias the stationary seal element against the rotating seal element, that are supported on their inside diameters, that are not subject to clogging, that are located externally of the process fluid environment so as to be removed from corrosive environments, and that are subject to complete visual inspection.
It is common in integrated or cartridge-type mechanical seal designs, for ease of installation, to employ some sort of setting clips that basically hold the rotary and stationary components together while the seal is installed to minimize installation time and misalignment of components. Many existing designs utilize setting clips that are rigidly secured to the various seal parts using screws or other fasteners. Obviously, these clip types with their fasteners must be repositioned or removed prior to operation of the seal. There are yet other designs that utilize removable, flexible setting straps or a setting means made of a wearable material, the latter not requiring removal.
It would clearly be desirable to have a cartridge-type assembly that utilizes wearable setting clips and therefore is easily installed, that holds the components of the seal assembly together in both axial directions along the shaft and concentrically positions the rotary parts relative to the stationary parts prior to and during installation, and that need not be repositioned or removed prior to operation of the mechanical seal.
Mechanical seals of the type under consideration include a gland assembly that is used to secure and seal the mechanical seal assembly to the housing through which the shaft extends. For example, in a typical use of a mechanical seal to effect sealing of a pump shaft, the gland is positioned around the pump shaft and secured by bolts to the pump housing. Typically, this is accomplished by means of threaded bolts that are received in threaded bores in the pump housing and extend through suitable apertures in the gland body or in tabs or lugs carried by the gland body of the mechanical seal. When the tabs or lugs are monolithic with the gland or must be installed as part of the gland, difficulty is often encountered because of tight spacing. Accordingly, it would clearly be desirable to have a gland assembly for use with a mechanical seal, which would allow the gland assembly to be positioned on the shaft and have removable tabs or lugs, which, once the gland is positioned on the shaft, can be easily affixed to the gland, following which the tabs or lugs can be used to secure the gland to the housing as described above.